Recently speeding up of color image forming is demanded, and a color toner to obtain a color image with high speed stably is also demanded.
When an image is formed with high speed as low cost printing, running speed through a fixing nip portion in the fixing device is so short that pressure and heating energy to endow the toner is reduced, and glossiness is insufficient or uneven glossiness is generated and the obtained image is inferior to images by low cost printing.
Lower temperature fixing method has been investigated to reduce consumption energy by a fixing device which requires largest energy consumed in an electrophotographic image forming apparatus in view of energy saving program. Toner should melt at lower temperature to attain lower temperature fixing, and for this purpose it has been provided to reduce melt viscosity of toner by employing resin having low glass transition temperature or smaller molecular weight generally.
Toner of lower melt viscosity has large of toner viscoelasticity around fixing temperature, and therefore, there is a problem that image glossiness tends to be uneven or may causes irregular glossiness.
When a toner of lower melt viscosity is employed in a high speed image forming apparatus, running speed through a fixing nip portion in the fixing device is so short that pressure and heating energy to endow the toner is reduced, and glossiness is insufficient or uneven glossiness is generated and the obtained image is inferior to images by low cost printing.
Though an improving method in view of storage modulus of toner is provided, it has not become sufficient to satisfy the high demand of the market (Patent Documents 1 and 2).    Patent Document 1: JP A 2D06-084952    Patent Document 2: JP A 2006-133451